1. Field of the Invention
The present invention relates to multi-layer substrates and satellite broadcast reception apparatuses including the multi-layer substrate, and receiving a weak electric wave from a satellite, amplifying the electric wave via a low noise amplifier, converting the wave to an intermediate frequency signal and amplifying it (hereinafter referred to as a low noise block-down (LNB) converter).
2. Description of the Background Art
FIG. 43 is an resolved view of a configuration of an LNB converter 130 for one polarized wave reception, by way of example. A weak signal transmitted from a satellite is received at an electric wave receiving portion 116. The received signal is propagated through a waveguide 113 and received by a probe 120 soldered to a double-sided substrate 110 substantially perpendicularly, and then transmitted to a low noise amplifier. Probe 120 penetrates substrate 110 through a hole 110a provided in the substrate for attaching the probe, and received by a hole 111a provided in a chassis 111 to receive the probe.
The double-sided substrate 110 ground layer 102 and chassis 111 are arranged to contact each other, as shown in FIG. 44. For a double-sided substrate, a microstrip line is formed between first and second layers 101 and 102 and the second layer 102 serving as a ground layer directly contacts chassis 111. Transit loss can be minimized without limit.
In recent years as satellite broadcast services have been diversified for example into such as multichannel services an LNB converter for example receiving electric waves from a plurality of satellites and in addition having a plurality of signal output terminals for transmission to a tuner has been produced. Such an LNB converter of course has a complicated circuit configuration. Conventionally when it is difficult to form such an LNB converter of a single double-sided substrate two or more double-sided substrates have been used and a joint pin or the like has been used to connect signal and power supply lines between the substrates.
Such an LNB converter, however, has a stereoscopic structure. It is also difficult to reduce in size and weight and produced by a complicated process. One approach to overcome these disadvantages is to use a 4-layer substrate. FIG. 45 is a cross section of a 4-layer substrate incorporated in an LNB converter. In FIG. 45 the 4-layer substrate includes two double-sided substrates bonded together by a bonding dielectric layer 106. A topmost, first layer is provided with signal and power supply lines 101a. A second layer 102 which and the first layer 101a together sandwich a dielectric layer 105, and a third layer 103 which and the second layer together sandwich a dielectric layer 106 are provided with ground layer. A ground layer for the signal and power supply lines is provided at a fourth layer 104. The fourth layer 104 is electrically connected to chassis 111.
The 4-layer substrate as described above allows reduced size and weight. The substrate can also dispense with a joint pin and the like and thus simplify the production process. However, as shown in FIGS. 46 and 47, grounds 103a, 104a of the third and fourth layers surrounding hole 110a having the probe passing therethrough, overlap, as seen in a plane. Hole 110a is surrounded by pattern clearances 103d, 104d and only throughhole lands 103b, 104b are isolated from the surrounding ground patterns, and there is not a substantial effect on the overlapping. The third and fourth layers' grounds of course also overlap the second, ground layer, as seen in a plane. As such, the second layer 102 serving as a ground layer in a microstrip line formed of the first layer 101a and the second layer 102 is in electrical contact with chassis 111 via the third, ground layer and the fourth layer's ground pattern 104.
As such, using in a portion receiving an electric signal from a waveguide a probe which is a component separate from a circuit board provides increased loss of transit characteristic for a specific reception frequency band, resulting the LNB converter providing unsatisfactory transit characteristic.